blocks|key|56563|text|如果你使用的是ActionBarActivity，那么你可以像这样告诉安卓使用Toolbar作为ActionBar：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|56564|Toolbar+toolbar+=+(Toolbar)+findViewById(R.id.my_awesome_toolbar);
setSupportActionBar(toolbar);|code-block|syntax|javascript|56565|然后调用|56566|getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);|56567|都会起作用的。您也可以在附加到ActionBarActivities的片段中使用它，您可以像这样使用它：|56568|((ActionBarActivity)+getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);
((ActionBarActivity)+getActivity()).getSupportActionBar().setDisplayShowHomeEnabled(true);|56569|如果您没有使用ActionBarActivities，或者如果您想要获取未设置为SupportActionBar的Toolbar上的后退箭头，则可以使用以下方法：|56570|mActionBar.setNavigationIcon(getResources().getDrawable(R.drawable.ic_action_back));
mActionBar.setNavigationOnClickListener(new+View.OnClickListener()+{
+++@Override
+++public+void+onClick(View+v)+{
+++++++//What+to+do+on+back+clicked
+++}
});|56571|如果您使用的是android.support.v7.widget.Toolbar，则应将以下代码添加到AppCompatActivity中|56572|@Override
public+boolean+onSupportNavigateUp()+{
++++onBackPressed();
++++return+true;
}|56573|entityMap^0|7|H|13|7|1C|9|0|0|0|0|F|J|0|0|7|J|14|G|1L|7|0|0|7|X|1F|H|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1A|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1C|8|@$9|1D|A|1E|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1F|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1G|8|@$9|1H|A|1I|B|C]|$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]]|D|@]|E|$]]|$1|U|3|V|5|H|7|1N|8|@]|D|@]|E|$I|J]]|$1|W|3|X|5|6|7|1O|8|@$9|1P|A|1Q|B|C]|$9|1R|A|1S|B|C]]|D|@]|E|$]]|$1|Y|3|Z|5|H|7|1T|8|@]|D|@]|E|$I|J]]|$1|10|3|-4|5|6|7|1U|8|@]|D|@]|E|$]]]|11|$]]

If you are using an <code>ActionBarActivity</code> then you can tell Android to use the <code>Toolbar</code> as the <code>ActionBar</code> like so:

<pre><code>Toolbar toolbar = (Toolbar) findViewById(R.id.my_awesome_toolbar);
setSupportActionBar(toolbar);
</code></pre>

And then calls to 

<pre><code>getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
</code></pre>

will work. You can also use that in Fragments that are attached to <code>ActionBarActivities</code> you can use it like this:

<pre><code>((ActionBarActivity) getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);
((ActionBarActivity) getActivity()).getSupportActionBar().setDisplayShowHomeEnabled(true);
</code></pre>

If you are not using <code>ActionBarActivities</code> or if you want to get the back arrow on a <code>Toolbar</code> that's not set as your <code>SupportActionBar</code> then you can use the following:

<pre><code>mActionBar.setNavigationIcon(getResources().getDrawable(R.drawable.ic_action_back));
mActionBar.setNavigationOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 //What to do on back clicked
 }
});
</code></pre>

If you are using <code>android.support.v7.widget.Toolbar</code>, then you should add the following code to your <code>AppCompatActivity</code>:

<pre><code>@Override
public boolean onSupportNavigateUp() {
 onBackPressed();
 return true;
}
</code></pre>

blocks|key|4563075|text|您可以使用工具栏的setNavigationIcon方法。Android+Doc|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4563076|mToolBar.setNavigationIcon(R.drawable.abc_ic_ab_back_mtrl_am_alpha);

mToolBar.setNavigationOnClickListener(new+View.OnClickListener()+{
++++@Override
++++public+void+onClick(View+v)+{
++++++++handleOnBackPress();
++++}
});|code-block|syntax|javascript|4563077|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/reference/android/widget/Toolbar.html#setNavigationIcon(android.graphics.drawable.Drawable)^0|T|B|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

you can use the tool bar setNavigationIcon method.
<a href="http://developer.android.com/reference/android/widget/Toolbar.html#setNavigationIcon(android.graphics.drawable.Drawable)" rel="noreferrer">Android Doc</a>

<pre><code>mToolBar.setNavigationIcon(R.drawable.abc_ic_ab_back_mtrl_am_alpha);

mToolBar.setNavigationOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 handleOnBackPress();
 }
});
</code></pre>

blocks|key|4563101|text|我看到了很多答案，但这里是我的答案，以前没有提到过。它通过8%2B接口工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4563102|public+class+DetailActivity+extends+AppCompatActivity

@Override
protected+void+onCreate(Bundle+savedInstanceState)+{
++++super.onCreate(savedInstanceState);
++++setContentView(R.layout.activity_detail);

++++//+toolbar
++++Toolbar+toolbar+=+(Toolbar)+findViewById(R.id.toolbar);
++++setSupportActionBar(toolbar);

++++//+add+back+arrow+to+toolbar
++++if+(getSupportActionBar()+!=+null){
++++++++getSupportActionBar().setDisplayHomeAsUpEnabled(true);
++++++++getSupportActionBar().setDisplayShowHomeEnabled(true);
++++}
}

@Override
public+boolean+onOptionsItemSelected(MenuItem+item)+{
++++//+handle+arrow+click+here
++++if+(item.getItemId()+==+android.R.id.home)+{
++++++++finish();+//+close+this+activity+and+return+to+preview+activity+(if+there+is+any)
++++}

++++return+super.onOptionsItemSelected(item);
}|code-block|syntax|javascript|4563103|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I see a lot of answers but here is mine which is not mentioned before. It works from API 8+.

<pre><code>public class DetailActivity extends AppCompatActivity

@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_detail);

 // toolbar
 Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
 setSupportActionBar(toolbar);

 // add back arrow to toolbar
 if (getSupportActionBar() != null){
 getSupportActionBar().setDisplayHomeAsUpEnabled(true);
 getSupportActionBar().setDisplayShowHomeEnabled(true);
 }
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
 // handle arrow click here
 if (item.getItemId() == android.R.id.home) {
 finish(); // close this activity and return to preview activity (if there is any)
 }

 return super.onOptionsItemSelected(item);
}
</code></pre>

blocks|key|56622|text|有很多方法可以做到这一点，下面是我最喜欢的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|56623|布局：|56624|<android.support.v7.widget.Toolbar
++++android:id="@%2Bid/toolbar"
++++android:layout_width="match_parent"
++++android:layout_height="?attr/actionBarSize"
++++app:navigationIcon="?attr/homeAsUpIndicator"+/>|code-block|syntax|javascript|56625|活动：|56626|Toolbar+toolbar+=+(Toolbar)+findViewById(R.id.toolbar);

toolbar.setNavigationOnClickListener(new+View.OnClickListener()+{
++++@Override
++++public+void+onClick(View+v)+{
++++++++//+back+button+pressed
++++}
});|56627|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

There are many ways to achieve that, here is my favorite:
Layout:
<pre><code>&lt;android.support.v7.widget.Toolbar
 android:id=&quot;@+id/toolbar&quot;
 android:layout_width=&quot;match_parent&quot;
 android:layout_height=&quot;?attr/actionBarSize&quot;
 app:navigationIcon=&quot;?attr/homeAsUpIndicator&quot; /&gt;
</code></pre>
Activity:
<pre class="lang-java prettyprint-override"><code>Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);

toolbar.setNavigationOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 // back button pressed
 }
});
</code></pre>

blocks|key|4563148|text|MyActivity+extends+AppCompatActivity+{

++++private+Toolbar+toolbar;

++++@Override
++++protected+void+onCreate(Bundle+savedInstanceState)+{
++++++++...
++++++++toolbar+=+(Toolbar)+findViewById(R.id.my_toolbar);
++++++++setSupportActionBar(toolbar);
++++++++getSupportActionBar().setDisplayHomeAsUpEnabled(true);
++++++++toolbar.setNavigationOnClickListener(arrow+->+onBackPressed());
++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4563149|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>MyActivity extends AppCompatActivity {

 private Toolbar toolbar;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 ...
 toolbar = (Toolbar) findViewById(R.id.my_toolbar);
 setSupportActionBar(toolbar);
 getSupportActionBar().setDisplayHomeAsUpEnabled(true);
 toolbar.setNavigationOnClickListener(arrow -&gt; onBackPressed());
 }
</code></pre>

blocks|key|56657|text|++++Toolbar+toolbar+=+(Toolbar)+findViewById(R.id.toolbar);
++++toolbar.setNavigationIcon(R.drawable.back_arrow);+//+your+drawable
++++toolbar.setNavigationOnClickListener(new+View.OnClickListener()+{
++++++++@Override
++++++++public+void+onClick(View+v)+{
++++++++++++onBackPressed();+//+Implemented+by+activity
++++++++}
++++});|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|56658|和21%2B+android:navigationIcon接口|unstyled|offset|length|style|CODE|56659|<android.support.v7.widget.Toolbar
++++android:navigationIcon="@drawable/back_arrow"
++++android:layout_width="match_parent"
++++android:layout_height="?attr/actionBarSize"/>|56660|entityMap^0|0|5|M|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|P|8|@$G|Q|H|R|I|J]]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|M|3|-4|5|F|7|T|8|@]|9|@]|A|$]]]|N|$]]

<pre><code> Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
 toolbar.setNavigationIcon(R.drawable.back_arrow); // your drawable
 toolbar.setNavigationOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 onBackPressed(); // Implemented by activity
 }
 });
</code></pre>

And for API 21+ <code>android:navigationIcon</code>

<pre><code>&lt;android.support.v7.widget.Toolbar
 android:navigationIcon="@drawable/back_arrow"
 android:layout_width="match_parent"
 android:layout_height="?attr/actionBarSize"/&gt;
</code></pre>

blocks|key|4563202|text|我在Google+Developer+Documentation中使用了这个方法|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4563203|@Override
public+void+onCreate(Bundle+savedInstanceState)+{
++...
++getActionBar().setDisplayHomeAsUpEnabled(true);
}|code-block|syntax|javascript|4563204|如果你得到一个空指针异常，它可能取决于主题。尝试在清单中使用不同的主题，或者使用以下内容：|4563205|@Override
public+void+onCreate(Bundle+savedInstanceState)+{
++...
++getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}|4563206|然后在清单中，我为当前活动设置了父活动：|4563207|<activity
++++++++android:name="com.example.myapp.MyCurrentActivity"
++++++++android:label="@string/title_activity_display_message"
+++++android:parentActivityName="com.example.myfirstapp.MainActivity"+>
++++
++++<meta-data
++++++++android:name="android.support.PARENT_ACTIVITY"
++++++++android:value="com.example.myapp.MyMainActivity"+/>
</activity>|4563208|我希望这能对你有所帮助！|4563209|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.android.com/training/implementing-navigation/ancestral.html^0|2|U|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|D|3|E|5|F|7|14|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|15|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|16|8|@]|9|@]|C|$G|H]]|$1|M|3|N|5|6|7|17|8|@]|9|@]|C|$]]|$1|O|3|P|5|F|7|18|8|@]|9|@]|C|$G|H]]|$1|Q|3|R|5|6|7|19|8|@]|9|@]|C|$]]|$1|S|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|T|$U|$5|V|W|X|C|$Y|Z]]]]

I used this method from the <a href="https://developer.android.com/training/implementing-navigation/ancestral.html" rel="noreferrer">Google Developer Documentation</a>:

<pre><code>@Override
public void onCreate(Bundle savedInstanceState) {
 ...
 getActionBar().setDisplayHomeAsUpEnabled(true);
}
</code></pre>

If you get a null pointer exception it could depend on the theme. Try using a different theme in the manifest or use this alternatively:

<pre><code>@Override
public void onCreate(Bundle savedInstanceState) {
 ...
 getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
</code></pre>

Then in the manifest, where I set the parent activity for current activity:

<pre><code>&lt;activity
 android:name="com.example.myapp.MyCurrentActivity"
 android:label="@string/title_activity_display_message"
 android:parentActivityName="com.example.myfirstapp.MainActivity" &gt;
 &lt;!-- Parent activity meta-data to support 4.0 and lower --&gt;
 &lt;meta-data
 android:name="android.support.PARENT_ACTIVITY"
 android:value="com.example.myapp.MyMainActivity" /&gt;
&lt;/activity&gt;
</code></pre>

I hope this will help you!

blocks|key|56771|text|如果您不想创建自定义Toolbar，可以这样做|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|56772|public+class+GalleryActivity+extends+AppCompatActivity+{

++++@Override
++++public+void+onCreate(Bundle+savedInstanceState)+{
++++++++...++
++++++++getSupportActionBar().setTitle("Select+Image");
++++++++getSupportActionBar().setDisplayHomeAsUpEnabled(true);
++++++++getSupportActionBar().setDisplayShowHomeEnabled(true);
++++}

++++@Override
++++public+boolean+onOptionsItemSelected(MenuItem+item)+{
++++++++if+(item.getItemId()+==+android.R.id.home)+{
++++++++++++finish();
++++++++}
++++++++return+super.onOptionsItemSelected(item);
++++}
}+++++++++++++++++++++|code-block|syntax|javascript|56773|In+you+AndroidManifest.xml|56774|<activity
++++android:name=".GalleryActivity"
++++android:theme="@style/Theme.AppCompat.Light">++++++++
</activity>|56775|您还可以将此android:theme="@style/Theme.AppCompat.Light"放入<aplication>标记，以便应用于所有活动|56776|​|56777|📷|atomic|56778|56779|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/9d05b16b1172aa73d2e031f71b87bbbd.png|imageAlt^0|A|7|0|0|7|J|0|0|6|18|1G|C|0|0|0|1|0|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|18|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1D|8|@$9|1E|A|1F|B|C]|$9|1G|A|1H|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1I|8|@]|D|@]|E|$]]|$1|S|3|T|5|U|7|1J|8|@]|D|@$9|1K|A|1L|1|1M]]|E|$]]|$1|V|3|R|5|6|7|1N|8|@]|D|@]|E|$]]|$1|W|3|-4|5|6|7|1O|8|@]|D|@]|E|$]]]|X|$Y|$5|Z|10|11|E|$12|13|14|-4]]]]

If you don't want to create a custom <code>Toolbar</code>, you can do like this

<pre><code>public class GalleryActivity extends AppCompatActivity {

 @Override
 public void onCreate(Bundle savedInstanceState) {
 ... 
 getSupportActionBar().setTitle("Select Image");
 getSupportActionBar().setDisplayHomeAsUpEnabled(true);
 getSupportActionBar().setDisplayShowHomeEnabled(true);
 }

 @Override
 public boolean onOptionsItemSelected(MenuItem item) {
 if (item.getItemId() == android.R.id.home) {
 finish();
 }
 return super.onOptionsItemSelected(item);
 }
} 
</code></pre>

In you <code>AndroidManifest.xml</code>

<pre><code>&lt;activity
 android:name=".GalleryActivity"
 android:theme="@style/Theme.AppCompat.Light"&gt; 
&lt;/activity&gt;
</code></pre>

you can also put this <code>android:theme="@style/Theme.AppCompat.Light"</code> to <code>&lt;aplication&gt;</code> tag, for apply to all activities

<a href="https://i.stack.imgur.com/bIrXI.png" rel="noreferrer"><img src="https://i.stack.imgur.com/bIrXI.png" alt="enter image description here"></a>

blocks|key|4563313|text|例如，在AppCompatActivity中，您可以这样做|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4563314|public+class+GrandStatActivity+extends+AppCompatActivity+{

++++@Override
++++protected+void+onCreate(Bundle+savedInstanceState)+{
++++++++super.onCreate(savedInstanceState);
++++++++setContentView(R.layout.activity_grand_stat);
++++}

++++@Override
++++public+void+onResume()+{
++++++++super.onResume();

++++++++//+Display+custom+title
++++++++ActionBar+actionBar+=+this.getSupportActionBar();
++++++++actionBar.setTitle(R.string.fragment_title_grandstats);

++++++++//+Display+the+back+arrow
++++++++getSupportActionBar().setDisplayHomeAsUpEnabled(true);
++++++++getSupportActionBar().setDisplayShowHomeEnabled(true);
++++}

++++//+Back+arrow+click+event+to+go+to+the+parent+Activity
++++@Override
++++public+boolean+onSupportNavigateUp()+{
++++++++onBackPressed();
++++++++return+true;
++++}

}|code-block|syntax|javascript|4563315|entityMap^0|4|H|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

In the <code>AppCompatActivity</code> for example you can do

<pre><code>public class GrandStatActivity extends AppCompatActivity {

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_grand_stat);
 }

 @Override
 public void onResume() {
 super.onResume();

 // Display custom title
 ActionBar actionBar = this.getSupportActionBar();
 actionBar.setTitle(R.string.fragment_title_grandstats);

 // Display the back arrow
 getSupportActionBar().setDisplayHomeAsUpEnabled(true);
 getSupportActionBar().setDisplayShowHomeEnabled(true);
 }

 // Back arrow click event to go to the parent Activity
 @Override
 public boolean onSupportNavigateUp() {
 onBackPressed();
 return true;
 }

}
</code></pre>

blocks|key|4563343|text|在工具栏上显示后退按钮的简单方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4563344|将此代码粘贴到onCreate方法中|4563345|+if+(getSupportActionBar()+!=+null){

++++++++++++getSupportActionBar().setDisplayHomeAsUpEnabled(true);
++++++++++++getSupportActionBar().setDisplayShowHomeEnabled(true);
++++++++}|code-block|syntax|javascript|4563346|将此重写方法粘贴到onCreate方法之外|4563347|@Override
public+boolean+onOptionsItemSelected(MenuItem+item)+{
++++if(item.getItemId()==+android.R.id.home)+{

++++++++finish();
++++}
++++return+super.onOptionsItemSelected(item);
}|4563348|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Simple and easy way to show back button on toolbar

Paste this code in onCreate method 

<pre><code> if (getSupportActionBar() != null){

 getSupportActionBar().setDisplayHomeAsUpEnabled(true);
 getSupportActionBar().setDisplayShowHomeEnabled(true);
 }
</code></pre>

Paste this override method outside the onCreate method 

<pre><code>@Override
public boolean onOptionsItemSelected(MenuItem item) {
 if(item.getItemId()== android.R.id.home) {

 finish();
 }
 return super.onOptionsItemSelected(item);
}
</code></pre>

blocks|key|4563376|text|你可以轻松地做到这一点。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4563377|Toolbar+toolbar+=+(Toolbar)+findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
@Override
public+boolean+onSupportNavigateUp()+{
++++onBackPressed();
++++return+true;
}|code-block|syntax|javascript|4563378|致词：https://freakycoder.com/android-notes-24-how-to-add-back-button-at-toolbar-941e6577418e|offset|length|4563379|entityMap|0|LINK|mutability|MUTABLE|url|https://freakycoder.com/android-notes-24-how-to-add-back-button-at-toolbar-941e6577418e^0|0|0|3|2F|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Easily you can do it.

<pre><code>Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
@Override
public boolean onSupportNavigateUp() {
 onBackPressed();
 return true;
}
</code></pre>

Credits:
<a href="https://freakycoder.com/android-notes-24-how-to-add-back-button-at-toolbar-941e6577418e" rel="noreferrer">https://freakycoder.com/android-notes-24-how-to-add-back-button-at-toolbar-941e6577418e</a>

blocks|key|56991|text|在Kotlin中，它将是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|56992|private+fun+setupToolbar(){
++++toolbar.title+=+getString(R.string.YOUR_TITLE)
++++setSupportActionBar(toolbar)
++++supportActionBar?.setDisplayHomeAsUpEnabled(true)
++++supportActionBar?.setDisplayShowHomeEnabled(true)
}

//+don't+forget+click+listener+for+back+button
override+fun+onSupportNavigateUp():+Boolean+{
++++onBackPressed()
++++return+true
}|code-block|syntax|javascript|56993|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<h2>In Kotlin it would be</h2>

<pre><code>private fun setupToolbar(){
 toolbar.title = getString(R.string.YOUR_TITLE)
 setSupportActionBar(toolbar)
 supportActionBar?.setDisplayHomeAsUpEnabled(true)
 supportActionBar?.setDisplayShowHomeEnabled(true)
}

// don't forget click listener for back button
override fun onSupportNavigateUp(): Boolean {
 onBackPressed()
 return true
}
</code></pre>

blocks|key|4563467|text|将此代码添加到布局文件夹中活动的xml中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4563468|<android.support.design.widget.AppBarLayout
++++android:layout_width="match_parent"
++++android:layout_height="wrap_content"
++++android:theme="@style/AppTheme.AppBarOverlay">
++++<android.support.v7.widget.Toolbar
++++++++android:id="@%2Bid/prod_toolbar"
++++++++android:layout_width="match_parent"
++++++++android:layout_height="?attr/actionBarSize"
++++++++android:background="?attr/colorPrimary"
++++++++app:popupTheme="@style/AppTheme.PopupOverlay"+/>
</android.support.design.widget.AppBarLayout>|code-block|syntax|javascript|4563469|使工具栏可单击，将以下内容添加到onCreate方法：|4563470|Toolbar+toolbar+=+(Toolbar)+findViewById(R.id.prod_toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
toolbar.setNavigationOnClickListener(new+View.OnClickListener()+{
++++@Override
++++public+void+onClick(View+v)+{
++++++++finish();
++++}
});|4563471|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Add this to activity's xml in layout folder: 

<pre><code>&lt;android.support.design.widget.AppBarLayout
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:theme="@style/AppTheme.AppBarOverlay"&gt;
 &lt;android.support.v7.widget.Toolbar
 android:id="@+id/prod_toolbar"
 android:layout_width="match_parent"
 android:layout_height="?attr/actionBarSize"
 android:background="?attr/colorPrimary"
 app:popupTheme="@style/AppTheme.PopupOverlay" /&gt;
&lt;/android.support.design.widget.AppBarLayout&gt;
</code></pre>

Make toolbar clickable, add these to onCreate method:

<pre><code>Toolbar toolbar = (Toolbar) findViewById(R.id.prod_toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 finish();
 }
});
</code></pre>

blocks|key|57053|text|对于Kotlin，它变成了：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|57054|Xml：|57055|<include
android:id="@%2Bid/tbSignToolbar+"
layout="@layout/toolbar_sign_up_in"/>|code-block|syntax|javascript|57056|在您的活动中：|57057|setSupportActionBar(tbSignToolbar+as+Toolbar?)//tbSignToolbar+:id+of+your+toolbar+
supportActionBar?.setDisplayHomeAsUpEnabled(true)
supportActionBar?.setDisplayShowHomeEnabled(true)|57058|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

With Kotlin it became:

Xml:

<pre><code>&lt;include
android:id="@+id/tbSignToolbar "
layout="@layout/toolbar_sign_up_in"/&gt;
</code></pre>

In your Activity:-

<pre><code>setSupportActionBar(tbSignToolbar as Toolbar?)//tbSignToolbar :id of your toolbar 
supportActionBar?.setDisplayHomeAsUpEnabled(true)
supportActionBar?.setDisplayShowHomeEnabled(true)
</code></pre>

blocks|key|57120|text|如果您想要获取未设置为SupportActionBar的工具栏上的后退箭头：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|57121|(kotlin)|57122|val+resId+=+getResIdFromAttribute(toolbar.context,+android.R.attr.homeAsUpIndicator)
toolbarFilter.navigationIcon+=+ContextCompat.getDrawable(toolbar.context,+resId)
toolbarFilter.setNavigationOnClickListener+{+fragmentManager?.popBackStack()+}|code-block|syntax|javascript|57123|要从属性中获取res：|57124|@AnyRes
fun+getResIdFromAttribute(context:+Context,+@AttrRes+attr:+Int):+Int+{
++++if+(attr+==+0)+return+0
++++val+typedValueAttr+=+TypedValue()
++++context.theme.resolveAttribute(attr,+typedValueAttr,+true)
++++return+typedValueAttr.resourceId
}|57125|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

If you want to get the back arrow on a Toolbar that's not set as your SupportActionBar:

(kotlin)

<pre><code>val resId = getResIdFromAttribute(toolbar.context, android.R.attr.homeAsUpIndicator)
toolbarFilter.navigationIcon = ContextCompat.getDrawable(toolbar.context, resId)
toolbarFilter.setNavigationOnClickListener { fragmentManager?.popBackStack() }
</code></pre>

to get res from attributes:

<pre><code>@AnyRes
fun getResIdFromAttribute(context: Context, @AttrRes attr: Int): Int {
 if (attr == 0) return 0
 val typedValueAttr = TypedValue()
 context.theme.resolveAttribute(attr, typedValueAttr, true)
 return typedValueAttr.resourceId
}
</code></pre>

blocks|key|57144|text|如果您正在使用JetPack导航。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|57145|以下是MainActivity的布局|57146|<androidx.constraintlayout.widget.ConstraintLayout+xmlns:android="http://schemas.android.com/apk/res/android"
+++++++++++++++++++++++++++++++++++++++++++++++xmlns:app="http://schemas.android.com/apk/res-auto"
+++++++++++++++++++++++++++++++++++++++++++++++xmlns:tools="http://schemas.android.com/tools"
+++++++++++++++++++++++++++++++++++++++++++++++android:layout_width="match_parent"
+++++++++++++++++++++++++++++++++++++++++++++++android:layout_height="match_parent"
+++++++++++++++++++++++++++++++++++++++++++++++tools:context=".MainActivity">

<androidx.appcompat.widget.Toolbar
++++++++android:id="@%2Bid/toolBar"
++++++++app:layout_constraintTop_toTopOf="parent"
++++++++app:layout_constraintStart_toStartOf="parent"
++++++++app:layout_constraintEnd_toEndOf="parent"
++++++++android:layout_width="match_parent"
++++++++android:layout_height="wrap_content">

</androidx.appcompat.widget.Toolbar>

<fragment
++++++++android:id="@%2Bid/my_nav_host_fragment"
++++++++android:name="androidx.navigation.fragment.NavHostFragment"
++++++++android:layout_width="match_parent"
++++++++android:layout_height="0dp"
++++++++app:defaultNavHost="true"
++++++++app:layout_constraintTop_toBottomOf="@id/toolBar"
++++++++app:layout_constraintBottom_toTopOf="parent"
++++++++app:navGraph="@navigation/nav_graph"/>|code-block|syntax|javascript|57147|​|57148|在activity类的onCreate()中SetUp你的Activity中的工具栏，如下所示。|57149|val+navHostFragment+=+supportFragmentManager
++++++++.findFragmentById(R.id.my_nav_host_fragment)+as+NavHostFragment?+?:+return

val+navController+=+navHostFragment.findNavController()
val+toolBar+=+findViewById<Toolbar>(R.id.toolBar)
setSupportActionBar(toolBar)+//+To+set+toolBar+as+ActionBar
setupActionBarWithNavController(navController)|57150|如果需要，setupActionBarWithNavController(navController)将在toolBar上创建一个后退按钮，并处理backButton功能。如果需要编写CustomBack功能，请在片段onCreate()方法中创建callBack，如下所示|57151|val+callback+=+requireActivity().onBackPressedDispatcher.addCallback(this)+{
++++++++//+Handle+the+back+button+event
++++}|57152|来自文档：https://developer.android.com/guide/navigation/navigation-custom-back|offset|length|57153|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.android.com/guide/navigation/navigation-custom-back^0|0|0|0|0|0|0|0|0|5|1X|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|15|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|16|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|17|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|18|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|19|8|@]|9|@]|A|$G|H]]|$1|O|3|P|5|6|7|1A|8|@]|9|@]|A|$]]|$1|Q|3|R|5|F|7|1B|8|@]|9|@]|A|$G|H]]|$1|S|3|T|5|6|7|1C|8|@]|9|@$U|1D|V|1E|1|1F]]|A|$]]|$1|W|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|X|$Y|$5|Z|10|11|A|$12|13]]]]

If you are using JetPack Navigation.

Here is the layout for MainActivity

<pre><code>&lt;androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:app="http://schemas.android.com/apk/res-auto"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 tools:context=".MainActivity"&gt;

&lt;androidx.appcompat.widget.Toolbar
 android:id="@+id/toolBar"
 app:layout_constraintTop_toTopOf="parent"
 app:layout_constraintStart_toStartOf="parent"
 app:layout_constraintEnd_toEndOf="parent"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"&gt;

&lt;/androidx.appcompat.widget.Toolbar&gt;

&lt;fragment
 android:id="@+id/my_nav_host_fragment"
 android:name="androidx.navigation.fragment.NavHostFragment"
 android:layout_width="match_parent"
 android:layout_height="0dp"
 app:defaultNavHost="true"
 app:layout_constraintTop_toBottomOf="@id/toolBar"
 app:layout_constraintBottom_toTopOf="parent"
 app:navGraph="@navigation/nav_graph"/&gt;
</code></pre>



SetUp your toolbar in your activity like below in onCreate() of your Activity class.

<pre><code>val navHostFragment = supportFragmentManager
 .findFragmentById(R.id.my_nav_host_fragment) as NavHostFragment? ?: return

val navController = navHostFragment.findNavController()
val toolBar = findViewById&lt;Toolbar&gt;(R.id.toolBar)
setSupportActionBar(toolBar) // To set toolBar as ActionBar
setupActionBarWithNavController(navController)
</code></pre>

setupActionBarWithNavController(navController) Will create a back button on the toolBar if needed and handles the backButton functionality.
If you need to write a CustomBack functionality, create a callBack as below on your fragment onCreate() method

<pre><code>val callback = requireActivity().onBackPressedDispatcher.addCallback(this) {
 // Handle the back button event
 }
</code></pre>

From Documentation:<a href="https://developer.android.com/guide/navigation/navigation-custom-back" rel="nofollow noreferrer">https://developer.android.com/guide/navigation/navigation-custom-back</a>

blocks|key|57183|text|首先，您需要初始化工具栏：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|57184|Toolbar+toolbar+=+(Toolbar)+findViewById(R.id.toolbar);
setSupportActionBar(toolbar);|code-block|syntax|javascript|57185|然后调用操作栏中的后退按钮：|57186|getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);

@Override
public+boolean+onSupportNavigateUp()+{
++++onBackPressed();
++++return+true;
}|57187|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

First, you need to initialize the toolbar :

<pre><code>Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
</code></pre>

then call the back button from the action bar :

<pre><code>getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);

@Override
public boolean onSupportNavigateUp() {
 onBackPressed();
 return true;
}
</code></pre>

blocks|key|57228|text|从你的主题中获取up图标可能是一个更可靠的方法(如果不使用工具栏作为你的操作栏)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|57229|toolbar.navigationIcon+=+context.getDrawableFromAttribute(R.attr.homeAsUpIndicator)|code-block|syntax|javascript|57230|为了将主题属性转换为可绘制的，我使用了一个扩展函数：|57231|fun+Context.getDrawableFromAttribute(attributeId:+Int):+Drawable+{
++++val+typedValue+=+TypedValue().also+{+theme.resolveAttribute(attributeId,+it,+true)+}
++++return+resources.getDrawable(typedValue.resourceId,+theme)
}|57232|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Possibly a more reliable way to get the up icon from your theme (if not using the toolbar as your action bar):

<pre><code>toolbar.navigationIcon = context.getDrawableFromAttribute(R.attr.homeAsUpIndicator)
</code></pre>

In order to turn the theme attribute into a drawable I used an extension function:

<pre><code>fun Context.getDrawableFromAttribute(attributeId: Int): Drawable {
 val typedValue = TypedValue().also { theme.resolveAttribute(attributeId, it, true) }
 return resources.getDrawable(typedValue.resourceId, theme)
}
</code></pre>

blocks|key|57285|text|如果您使用的是androidx.appcompat.app.AppCompatActivity，只需使用：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|57286|Toolbar+toolbar+=+findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);|code-block|syntax|javascript|57287|然后只需在Manifest.xml中定义父活动即可。|57288|<activity
++++android:name=".MyActivity"
++++...>
++<meta-data
++++++android:name="android.support.PARENT_ACTIVITY"
++++++android:value=".ParentActivity"+/>
</activity>|57289|相反，如果您使用的是Toolbar，并且想要自定义行为，则只需使用：|57290|<androidx.appcompat.widget.Toolbar
++++android:id="@%2Bid/toolbar"+
++++app:navigationIcon="?attr/homeAsUpIndicator"
++++.../>|57291|在你的活动中：|57292|Toolbar+toolbar+=+(Toolbar)+findViewById(R.id.toolbar);
toolbar.setNavigationOnClickListener(new+View.OnClickListener()+{
++++@Override
++++public+void+onClick(View+v)+{
++++++++//....
++++}
});|57293|entityMap^0|7|14|0|0|5|C|0|0|A|7|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1A|8|@]|D|@]|E|$]]|$1|U|3|V|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|W|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|X|$]]

If your are using the <code>androidx.appcompat.app.AppCompatActivity</code> just use:

<pre><code>Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
</code></pre>

Then just define in the <code>Manifest.xml</code> the parent Activity.

<pre><code>&lt;activity
 android:name=".MyActivity"
 ...&gt;
 &lt;meta-data
 android:name="android.support.PARENT_ACTIVITY"
 android:value=".ParentActivity" /&gt;
&lt;/activity&gt;
</code></pre>

Instead if you are using a <code>Toolbar</code> and you want a custom behavior just use:

<pre><code>&lt;androidx.appcompat.widget.Toolbar
 android:id="@+id/toolbar" 
 app:navigationIcon="?attr/homeAsUpIndicator"
 .../&gt;
</code></pre>

and in your Activity:

<pre><code>Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 //....
 }
});
</code></pre>

blocks|key|4563719|text|也许它会帮助一些人，我没有在软件中找到我最后做的事情:使用ActionBarDrawerToggle+mDrawerToggle；在工具栏集中显示向后箭头:+mDrawerToggle.setDrawerIndicatorEnabled(false)；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4563720|如果你想让它在工具栏中显示汉堡：|4563721|mDrawerToggle.setDrawerIndicatorEnabled(true)；|4563722|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

maybe it will help someone,I didn't find in the answares the thing I did by the end:
with ActionBarDrawerToggle mDrawerToggle;
to show the back arrow in toolbar set:
mDrawerToggle.setDrawerIndicatorEnabled(false);
and if you want it to show the hamburger in the toolbar:
mDrawerToggle.setDrawerIndicatorEnabled(true);

blocks|key|4563824|text|如果你想要快速简单地处理你的问题，请遵循3个步骤：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4563825|使用下面的代码将文件ic_arrow.xml添加到可绘制文件夹(将下面的代码添加到ic_arrow.xml中)|4563826|<?xml+version="1.0"+encoding="utf-8"?>
<vector+xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:width="24dp"
android:height="24dp"
android:tint="@color/black"
android:viewportWidth="24"
android:viewportHeight="24"
tools:ignore="ExtraText">
<path
++++android:fillColor="@android:color/white"
++++android:pathData="M20,11H7.83l5.59,-5.59L12,4l-8,8+8,8+1.41,-1.41L7.83,13H20v-2z"+/>
</vector>|code-block|syntax|javascript|4563827|将ImageButton添加到Toolbar+(确保工具栏是自定义的，而不是标题栏或状态栏)-如果需要，您可以自定义ImageButton+(箭头按钮)位置|offset|length|style|CODE|4563828|<ImageButton
android:id="@%2Bid/arrow"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_arrow"
android:layout_marginTop="15dp"
android:layout_marginStart="15dp"
android:background="@android:color/transparent"
tools:ignore="ContentDescription"+/>|4563829|将setArrowButton方法添加到DetailActivity.java+(或所需的任何xxxActivity.java+)|4563830|public+class+DetailActivity+extends+AppCompatActivity+{
++++ImageButton+arrowButton;

++++@Override
++++protected+void+onCreate(Bundle+savedInstanceState)+{
++++super.onCreate(savedInstanceState);
++++setContentView(R.layout.activity_detail);

++++arrowButton+=+findViewById(R.id.arrow);

++++setArrowButton(arrowButton);
}

public+void+setArrowButton(ImageButton+arrowButton)+{
++++arrowButton.setOnClickListener(new+View.OnClickListener()+{
++++++++@Override
++++++++public+void+onClick(View+view)+{
++++++++++++finish();+//will+close+the+moment+activity+and+return+to+
++++++++++++++++++++++//the+last+activity
++++++++}
++++});
+++}
}|4563831|完成|4563832|关于arrowButton的预览|4563833|​|4563834|📷|atomic|4563835|4563836|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/ed0f5b17492be8280bf9a2e79266e788.png|imageAlt^0|0|0|0|1|B|F|7|0|0|1|E|K|J|0|0|0|0|0|0|1|0|0|0^^$0|@$1|2|3|4|5|6|7|1D|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1E|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1F|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|1G|8|@$K|1H|L|1I|M|N]|$K|1J|L|1K|M|N]]|9|@]|A|$]]|$1|O|3|P|5|F|7|1L|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|1M|8|@$K|1N|L|1O|M|N]|$K|1P|L|1Q|M|N]]|9|@]|A|$]]|$1|S|3|T|5|F|7|1R|8|@]|9|@]|A|$G|H]]|$1|U|3|V|5|6|7|1S|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1T|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|1U|8|@]|9|@]|A|$]]|$1|10|3|11|5|12|7|1V|8|@]|9|@$K|1W|L|1X|1|1Y]]|A|$]]|$1|13|3|Z|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|14|3|-4|5|6|7|20|8|@]|9|@]|A|$]]]|15|$16|$5|17|18|19|A|$1A|1B|1C|-4]]]]

Follow 3 steps if you want to handle your problem fastly &amp; simply:
Add file ic_arrow.xml to Drawable folder with some codes below (add codes below into ic_arrow.xml)
<pre><code>&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;vector xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
xmlns:tools=&quot;http://schemas.android.com/tools&quot;
android:width=&quot;24dp&quot;
android:height=&quot;24dp&quot;
android:tint=&quot;@color/black&quot;
android:viewportWidth=&quot;24&quot;
android:viewportHeight=&quot;24&quot;
tools:ignore=&quot;ExtraText&quot;&gt;
&lt;path
 android:fillColor=&quot;@android:color/white&quot;
 android:pathData=&quot;M20,11H7.83l5.59,-5.59L12,4l-8,8 8,8 1.41,-1.41L7.83,13H20v-2z&quot; /&gt;
&lt;/vector&gt;
</code></pre>
Add <code>ImageButton</code> to <code>Toolbar</code> (make sure the Toolbar customized, not Titlebar or Statusbar) - You can customize the ImageButton (arrow button) position if you want
<pre><code>&lt;ImageButton
android:id=&quot;@+id/arrow&quot;
android:layout_width=&quot;wrap_content&quot;
android:layout_height=&quot;wrap_content&quot;
android:src=&quot;@drawable/ic_arrow&quot;
android:layout_marginTop=&quot;15dp&quot;
android:layout_marginStart=&quot;15dp&quot;
android:background=&quot;@android:color/transparent&quot;
tools:ignore=&quot;ContentDescription&quot; /&gt;
</code></pre>
Add the <code>setArrowButton</code> method to <code>DetailActivity.java</code> (or any xxxActivity.java that you need)
<pre><code>public class DetailActivity extends AppCompatActivity {
 ImageButton arrowButton;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_detail);

 arrowButton = findViewById(R.id.arrow);

 setArrowButton(arrowButton);
}

public void setArrowButton(ImageButton arrowButton) {
 arrowButton.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View view) {
 finish(); //will close the moment activity and return to 
 //the last activity
 }
 });
 }
}
</code></pre>
Done
Preview about arrowButton
<a href="https://i.stack.imgur.com/ciwH1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ciwH1.png" alt="enter image description here" /></a>

I'm migrating from <code>ActionBar</code> to <code>Toolbar</code> in my application. 
But I don't know how to display and set click event on Back Arrow on <code>Toolbar</code> like I did on <code>Actionbar</code>. 

<img src="https://i.stack.imgur.com/avYnD.png" alt="enter image description here">

With <code>ActionBar</code>, I call <code>mActionbar.setDisplayHomeAsUpEnabled(true)</code>.
But there is no the similar method like this.

Has anyone ever faced this situation and somehow found a way to solve it?

Display Back Arrow on Toolbar

Kotlin

我要在我的应用程序中从ActionBar迁移到Toolbar。但我不知道如何像在Actionbar上那样在Toolbar上显示和设置后退箭头上的单击事件。​​使用ActionBar时，我调用mActionbar.setDisplayHomeAsUpEnabled(true)。但是没有类似的方法。有没有人曾经面对过这种情...

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